Question

Henry Ford adapted the assembly line to make cars. The assembly line is an innovation in factory production.

Answer 1

D. Henry Ford adapted the assembly line, an innovation in factory production, to produce cars.

Answer 2

The answer is 3: Henry Ford adapted the assembly line, an innovation in factory prodution, to produce cars.

 An appositive phrase is a noun phrase that adds importantl information or adds descriptive words that help make the sentence more detailed. But the information can be removed without changing the grammar and meaning of the sentence: "Henry Ford adapted the assembly line to produce cars." the appositive sentence is only describing what assembly line is.